The applicants have proposed to develop an inexpensive device that rapidly measures the body density (in air) of non-infant children and adults so that a quantitative degree of obesity (body fat fraction) may be deduced. Such routine measurements should result in improved weight control programs with consequent reduction in the health risks associated with hypertension, cardio vascular disease, cancer, diabetes, and many other disorders. There are two known methods that have been proposed for the in-air measurement of body volume - principally for infants. One is based on air displacement and the intrinsic relationship between gas volume and pressure. Another method using the Helmholtz resonator principal with excitation from a loud-speaker has also been proposed for infants. Both methods are complex and highly sensitive to temperature. The proposed new device also uses acoustic resonance principles but eliminates problems related to temperature or humidity changes. It is expected that very accurate measurements can be made in much less than a minute with readout in body density and estimated percent body fat. The device should be inexpensive and a product desired and eventually required by most physicians. Specific aims of Phase I would include design and construction of a breadboard acoustic volume device to measure the volume of adults and optimize the system by measuring a range of known volumes of water. Some preliminary studies would also be conducted with some human volunteers.